The prospective study will enroll a cohort of approximately 1500 pregnant Hispanic women attending prenatal care services through an OB/GYN group at the San Joaquin General Hospital in Stockton, CA. The majority of Hispanic women (67%) receiving prenatal care through this group are Mexican immigrants of varying lengths of US residency, and up to 26% of them are involved in farm labor and/or other types of manual labor. Eighteen percent are US-born Mexican women. A study of this unique population of Hispanic women of varying lengths of US residency, and factors related to occupational risks, acculturation and preterm low birth weight deliveries, will provide an excellent opportunity to examine the factors of acculturation-based causes of preterm low birthweight (PTLBW).